Electric generator system for speed indicators



Uite rates Pater 0 ELECTRIC GENERATOR SYSTEM FOR SPEED INDICATQRS Sidney Davis, Brooklyn, N. Y., assignor to American Bosch Arma Corporation Application April 5, 1951, Serial No. 219,417 2 Claims. (61!. 322-96) shaft. In many cases the voltage gradients for opposite directions of rotation may difier and this defect becomes serious where reasonable precision is desired or where the tachometer output is used as a part of a computing device.

The present invention equalizes the voltage gradients by inserting a unilateral resistor between the tachometer and the load. In a preferred embodiment of this invention a fixed series resistor is connected between the generator and the load and a variable resistor and rectifier are con uected across the load terminals.

By proper adjustment of the variable resistor and proper choice of the polarity of the rectifier the voltage gradients at the load may be equalized for both directions of rotation.

For a more complete understanding of this invention, reference may be had to the accompanying drawing, which is a schematic wiring diagram of the preferred embodiment.

With reference to the figure, numeral 19 designates generally a conventional tachometer-generator, the armature 11 of which is driven by the shaft l2 whose rotational velocity is to be determined. The armature 11 is supported by frame 13 and rotates within the magnetic field provided by permanent magnets 14. Brushes 15 co operate with the commutator 16 to produce a unidirectional voltage across brushes 15 proportional in magnitude to the rotational velocity of armature 11. In most cases,

however, a difference in the voltage gradient i. e. the ratio of voltage output to speed, exists for the opposite direc tions of rotation, hereafter called the plus and minus rotations.

In order to equalize the voltage gradients a network 17 which is shown within the dotted line 17a is connected bemisses The network 17 is preferably an L type network in which the series arm is a fixed resistor 19 interposed in line 22 and the shunting arm contains a variable resistor Ztl and a rectifying device 21 connected to output lines 22 and 23 across the load 13.

The operation of the invention may be seen by assuming, for example, that the voltage gradient for plus rotation of armature 11 is greater than the voltage gradient for minus rotation. This can be determined by use of a voltmeter. In order to equalize the voltage gradients across the load 18, the voltage drop across resistor 19 must be increased for a plus rotation of armature if. over that due to the greater induced voltage at brushes 15. Therefore, the polarity of rectifier 21 is such that current flows through the resistor 2i only during plus rotation of armature 11. The magnitude of the change in voltage If it is found that the resistance of armature ii is sufficiently large to provide the correction as described, when used as the series arm resistance of network 17, the re sister 19 may be omitted.

Although only one circuit has been illustrated and described, other arrangements which are essentially equal rotation at any one speed.

2. The device of claim 1 in which a fixed resistance is in series with the load on the generator side of said network so as to receive the full flow of current regardless of the direction of rotation of said armature.

References Cited in the file of this patent UNITED STATES PATENTS 1,096,942 Owens May 19, 1914 1,816,748 Romain July 28, 1931 2,076,962 OHagan Apr. 13, 1937 2,284,423 Hansell May 26, I942 July 19, 1955 w. L. R. HENDERSON REACTOR Filed Feb. 19, 1954 INVENTOR. fienczerson Way/76L.

BY M ///.'s Attorney. 

